diff --git a/types/fast64/fast64-tests.ts b/types/fast64/fast64-tests.ts
new file mode 100644
index 0000000000..f038b9d0a8
--- /dev/null
+++ b/types/fast64/fast64-tests.ts
@@ -0,0 +1,8 @@
+import * as fast64 from "fast64";
+
+fast64.encode(""); // $ExpectType string
+fast64.decode(""); // $ExpectType string
+fast64.decode("", { uint8Array: true }); // $ExpectType Uint8Array
+fast64.urlencode(""); // $ExpectType string
+fast64.urldecode(""); // $ExpectType string
+fast64.urldecode("", { uint8Array: true }); // $ExpectType Uint8Array
diff --git a/types/fast64/index.d.ts b/types/fast64/index.d.ts
new file mode 100644
index 0000000000..47f067859c
--- /dev/null
+++ b/types/fast64/index.d.ts
@@ -0,0 +1,15 @@
+// Type definitions for fast64 0.5
+// Project: https://github.com/superhuman/fast64
+// Definitions by: Rares Matei <https://github.com/rarmatei>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+export interface Options {
+    uint8Array: boolean;
+}
+
+export function encode(value: string): string;
+export function decode(base64: string): string;
+export function decode(base64: string, options: Options): Uint8Array;
+export function urlencode(value: string): string;
+export function urldecode(base64: string): string;
+export function urldecode(base64: string, options: Options): Uint8Array;
diff --git a/types/fast64/tsconfig.json b/types/fast64/tsconfig.json
new file mode 100644
index 0000000000..4ad215d37c
--- /dev/null
+++ b/types/fast64/tsconfig.json
@@ -0,0 +1,23 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "strictFunctionTypes": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "fast64-tests.ts"
+    ]
+}
\ No newline at end of file
diff --git a/types/fast64/tslint.json b/types/fast64/tslint.json
new file mode 100644
index 0000000000..3db14f85ea
--- /dev/null
+++ b/types/fast64/tslint.json
@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }